The present invention relates to molding compositions useful for the preparation of water extended hydrophilic molded articles that are soft but yet structurally stable, tough and readily machined and polished. More particularly, the present invention relates to soft denture liners prepared from the molding composition which provide a soft cushion between the dental plate and the user's gums and which exhibit good adhesion to a dental plate, toughness, and superior structural stability. Still more particularly, the present invention relates to soft denture liners fabricated of water-extended, filled, crosslinked amide-endcapped alkylene oxide polymers.
At present, denture liners are utilized on a denture plate to provide a soft, smooth but firm contact with the user's gum so that the gums are not irritated by the plate. Various materials have been employed for this purpose, among which are plasticized waxes, polyvinyl chloride, soft acrylic polymers, silicone elastomers and hydrogels based on poly .beta.-(hydroxyethyl)methacrylate, commonly referred to as "Sofdent". Denture liners prepared of these materials have a short lifetime and are unsatisfactory for one or more other reasons. The wax liners are fragile and easily damaged. Liners of plasticized polyvinyl chloride are difficult to fabricate and the plasticizer migrates from the liner into the plate causing the liner to harden and crack and the plate to soften and deform. Soft acrylic liners have poor adhesion to the dental plate base and have low abrasion resistance. Silicone elastomer liners are difficult to fabricate and polish, take on stain, and may foul during use. The "Softdent" liners tend to pick up about 50% by weight of water upon soaking therein and undergo dimensional changes so that precise impressions made by the dentist no longer fit the wearer's mouth.
Consequently, there are no soft denture liners known to the applicants that are tough, comfortable, exhibit good dimensional stability and have a long life and yet are easy to fabricate and finish when on the dental plate.